Pitfalls and artifacts using the D-SPECT dedicated cardiac camera

Myocardial perfusion imaging is a well-established and widely used imaging technique for the assessment of patients with known or suspected coronary artery disease. Pitfalls and artifacts associated with conventional gamma cameras are well known, and the ways to avoid and correct them have been described. In recent years solid-state detector dedicated cardiac cameras were introduced and have been shown to offer improved accuracy in addition to new imaging protocols and novel applications. The purpose of this manuscript is to familiarize the readers with the causes and effects of technical, patient-related, and operator-related pitfalls and artifacts associated with the D-SPECT dedicated cardiac camera with solid-state detectors. The manuscript offers guidance on how to avoid these factors, how to detect them, and how to correct better for them, providing high-quality diagnostic images

The effect of energy and source location on gamma camera intrinsic and extrinsic spatial resolution: an experimental and Monte Carlo study.

Quantification of nuclear medicine image data is a prerequisite for personalized absorbed dose calculations and quantitative biodistribution studies. The spatial response of a detector is a governing factor affecting the accuracy of image quantification, and the aim of this work was to model this impact. To simulate spatial response, a value for the intrinsic spatial resolution (R(intrinsic)) of the gamma camera is needed. R(intrinsic) for (99m)Tc was measured over the field of view (FOV) and an experimental setup was designed to measure R(intrinsic) for radioisotopes with higher photon energies. Monte Carlo (MC) simulations, using the codes SIMIND and GATE, were used to investigate the extrinsic effect of R(intrinsic) as a function of energy and its variation across the FOV. A method was developed to calculate energy-dependent blurring values for input to MC simulations, by separate consideration of the Compton scatter and photoelectric effect in the crystal and statistical variation in the signal. Inclusion of energy-specific blurring values in simulations showed excellent agreement with experimental measurements. The maximum pixel count rate can change by up to 18% when imaged at two different points in the FOV, and errors in the maximum pixel count rate of up to 11% were shown if a blurring value for (99m)Tc was used for simulations of (131)I. We demonstrate that the accuracy of MC simulations of gamma cameras can be significantly improved by accounting for the effect of energy on intrinsic spatial resolution

Optimization of energy-window settings for scatter correction in quantitative (111)In imaging: comparison of measurements and Monte Carlo simulations.

Activity quantification in nuclear medicine imaging is highly desirable, particularly for dosimetry and biodistribution studies of radiopharmaceuticals. Quantitative (111)In imaging is increasingly important with the current interest in therapy using (90)Y radiolabeled antibodies. One of the major problems in quantification is scatter in the images, which leads to degradation of image quality. The aim of this study was to optimize the energy-window settings for quantitative (111)In imaging with a camera that enabled acquisition in three energy windows. Experimental measurements and Monte Carlo simulations, using the SI-MIND code, were conducted to investigate parameters such as sensitivity, image contrast, and image resolution. Estimated scatter-to-total ratios and distributions, as obtained by the different window settings, were compared with corresponding simulations. Results showed positive agreement between experimental measurements and results from simulations, both quantitatively and qualitatively. We conclude that of the investigated methods, the optimal energy-window setting was two windows centered at 171 and 245 keV, together with a broad scatter window located between the photopeaks

Clinical feasibility study to detect angiogenesis following bone marrow stem cell transplantation in chronic ischaemic heart failure

Background: Bone marrow stem cell (BMSC) therapy for cardiovascular disease has shown considerable preclinical and clinical promise, but there remains a need for mechanistic studies to help bridge the transition from bench to bedside. We have designed a substudy to our REGENERATE-IHD trial (ClinicalTrial.gov Identifier: NCT00747708) to assess the feasibility of a novel imaging technique to detect angiogenesis following BMSC therapy. Methods and Results: Nine patients who had been randomized to receive intracoronary injection of G-CSF-mobilized BMSCs or control (serum) were included in this substudy. Patients underwent SPECT imaging using a novel radiolabelled peptide (99mTc-NC100692), which has a high affinity for the αvβ3 integrin, an angiogenesis-related integrin. This was repeated 4 days after intracoronary injection of BMSCs/control to assess for neoangiogenesis. The imaging study was well tolerated with no adverse effects. Myocardial tracer uptake was detectable at baseline in all nine patients, with no myocardial uptake seen in two control patients used for comparison. Baseline uptake appeared to correlate with baseline ejection fraction but changes with therapy did not reach statistical significance. Conclusion: SPECT imaging with a 99mTc-NC100692 is feasible in patients with heart failure, with baseline activity suggesting persistent angiogenesis in patients with remote myocardial infarction